1. Field of the Invention
The present invention relates to a developer cartridge, a print process cartridge, and an image forming apparatus.
2. Description of the Art
Electrophotographic process is performed in a conventional image forming apparatus such as an electrophotographic printer, a copying machine, or a facsimile machine. A charging unit charges a circumferential surface of an image bearing body. An exposing unit such as a light emitting diode head (LED head) illuminates the charged circumferential surface of the image bearing body to form an electrostatic latent image. A developing unit supplies developer to the electrostatic latent image to develop it with the developer into a developer image. The developer image is transferred onto paper that is being advanced. The paper then enters a fixing unit where the developer image is fixed into a permanent image. Some of the developer may remain on the image bearing body after transfer of the developer image onto the paper. The residual developer is removed by a cleaning blade. A waste developer collecting unit transports the residual developer removed from the image bearing body. The residual developer is finally collected as a waste developer into a developer cartridge.
Such a conventional developer cartridge includes a fresh developer chamber that holds fresh developer to be supplied into a print process cartridge of the image forming apparatus and a waste developer chamber that holds the waste developer. Japanese patent publication (KOKAI) No. 2004-85894 discloses this type of developer cartridge and an image forming apparatus to which the developer cartridge is attached.
FIG. 13A illustrates a generally cylindrical developer cartridge 101 immediately before it is mounted to the print process cartridge 102.
The developer cartridge 101 includes a lid 104 that opens and closes an opening 101a from the inside of the developer cartridge 101, and a spring 104a that urges the lid 104 toward the opening 101a. The spring 104a has one end fixed to an inner wall that defines the opening 101a and another end fixed to the lid 104, and urges the lid 104 against the wall of the developer cartridge to close the opening 101a. 
FIG. 13B illustrates the print process cartridge 102 shortly after it is mounted to the print process cartridge 102. The print process cartridge 102 includes a waste developer discharging cylinder 103 to which the developer cartridge 101 is attached. The waste developer is collected into the developer cartridge 101 through the waste developer discharging cylinder 103. The discharging mechanism 103 includes an opening 103a through which the waste developer is discharged into the developer cartridge 101, a lid 105 that fits over the discharging cylinder 103b and is slidable in an axial direction of the discharging cylinder 103b. A spring 105a is mounted to the discharging cylinder 103 and urges the lid 105 toward a free end of the discharging cylinder 103b. 
The opening 101a of the developer cartridge 101 is a cylindrical hole having an inner diameter slightly larger than an outer diameter of the discharging cylinder 103b. When the developer cartridge 101 is out of the print process cartridge 102, the lid 104 closes the opening 101a of the developer cartridge 101 and the lid 105 closes the discharges cylinder 103b of the print process cartridge 102. Specifically, the spring 104a urges the lid 104 to close the opening 101a while the spring 105a urges the lid 105 to close the opening in the discharging cylinder 103b, so that the developer held in the developer cartridge 101 and in the discharging cylinder 103b is prevented from leaking out.
Prior to attachment of the developer cartridge to the print process cartridge 102, the developer cartridge 101 is tilted at an angle and is attached to the print process cartridge 102 so that the discharge cylinder 103b enters the opening 101a. Then, a user moves the developer cartridge 101 in a direction shown by arrow P to fit to the print process cartridge 102. At this moment, the side wall of the developer cartridge 101 pushes the lid 105 away from the free end in the axial direction of the discharging cylinder 103b, causing the opening 103a to be exposed. Then, as the user moves the developer cartridge 101 further, the discharging cylinder 103b enters the developer cartridge 101 through the opening 101a. The tip of the discharging cylinder 103b causes the lid 104 to slide into the developer cartridge 101 against the urging force of the spring 104a. 
As described above, the developer cartridge 101 is mounted to the print process cartridge 102. As shown in FIG. 13B, as long as the developer cartridge 101 remains attached to the print process cartridge 102, both the opening 101a and the opening 103a remain open. Thus, the waste developer in the discharging cylinder 103b is transported in a direction shown by arrow A (FIG. 13B), and falls into the developer cartridge 101 through the opening 103a. A spiral 106 transports the waste developer toward a far end of the developer cartridge 101.
FIG. 13C illustrates the cylindrical developer cartridge 101 when it is being detached from the print process cartridge 102.
When the developer cartridge 101 is detached from the print process cartridge 102, the developer cartridge 101 is first tilted at an angle with a horizontal direction, and is then pulled in a direction shown by arrow Q in FIG. 13C. When the developing cartridge 101 is pulled farther away from the print process cartridge 102, the urging force of the spring 104a causes the lid 104 to close the opening 101a and opening 103a while the urging force of the spring 105a causes the lid 105 to close the opening 103a. 
As described above, the developer cartridge 101 is tilted before it is detached from the print process cartridge 102.
FIGS. 14A and 14B illustrate the conventional developer cartridge 101 when the developer cartridge 101 is taken out of the print process cartridge 102.
Due to the inclination of the developer cartridge 101, the waste developer in the developer cartridge 101 tends to move toward the opening 101a and piles up in the vicinity of the opening 101a. If the waste developer reaches the lid 104, the waste developer will be pushed out of the developer cartridge 101.